Cable tap connections to coaxial cables for RF signals and computer data information traditionally have been provided by splicing into the cable. One way of providing splicing is to cut the cable and affix a male connector on each end of the severed cable. A terminal block having three parallel female connections, is used to connect the two spliced ends and to provide the additional cable tap signal path. Not only does this interrupt the signal path, causing an interruption in the data or signal transfer service, but also requires expensive machined connector parts, and careful assembly by skilled technicians. Moreover, if this connector is to be used in the external environment, each of those connectors requires a particular method of weatherproofing.
A second approach commonly used in the data network style coaxial connections is to clamp the cable in a fixture having two jaws, thus securing the cable therebetween. One of the two jaws has a threaded opening to receive a conical cable piercing signal probe along an axis perpendicular to the cable. The signal probe is then screwed into the cable to first displace the outer shield. The tip then proceeds through the dielectric of the cable until it comes in contact with the cable center conductor. However, since the probe provides a unilateral pressure on the center conductor of the cable, the pressure between the probe tip and the center conductor decreases with time due to material relaxation. Moreover, if the tap is not carefully applied, or if the cable suffers from variations in the alignment of the elements, such as the placement of the center wire, a signal probe will not properly contact the center cable. Additionally, while the probe tip is piercing the outer conductive shield, portions of it may be pulled through the dielectric, shorting out the center conductor. This short circuit condition, which may be temporary, can nonetheless cause a critical and serious disruption of service.
Another cable connector includes a second cable-piercing probe in contact with the center conductor and disposed in opposition to the signal probe. The additional probe may be spring-loaded to provide a constant force on the center conductor, and therefore a constant force between the center conductor and the signal probe. However, this too introduces a possibility of another temporary short circuit-condition during installation, and critically relies on the accuracy of the position of the cable center conductor. Moreover, the application of each cable-piercing pin presents a capacitive load to the cable of at least five picofarads, which may place an undesired load on the cable.
Drilling fixtures have also been suggested to reduce the additional capacitance or the likelihood of short circuits. However, since the axis of the drill is aligned perpendicular to the center wire so that the signal pins coincide therewith, the depths by which the cable is drilled, and location of the cable drill is critical, and must be carefully measured and controlled.